Controls on the Recycling and Preservation of Biogenic Silica from Biomineralization to Burial

The recycling of biogenic silica (bSiO(2)) produced by diatoms is a vital process sustaining a significant fraction of primary production in the oceans. The efficiency with which bSiO(2) dissolves controls the availability of nutrient silicon in the water column, and modulates the export of organic carbon to the deep sea. Environmental conditions during biomineralization (temperature, nutrient availability, light, etc.) affect the silicification and weathering resistance of diatom frustules, while ecosystem processes, including grazing and aggregation, are determining factors for the recycling of bSiO(2) in the water column. Bacterial colonization of dead diatoms leads to the decomposition of the protective organic layers allowing for the dissolution of bSiO(2) to begin. The dissolution rate of diatom frustules is a function of the physicochemical properties of both the silica (e. g., specific surface area, degree of hydration and condensation, impurities) and the aqueous medium (e. g., temperature, pH, pressure, electrolyte composition). In sediments, the dissolution of bSiO(2) is controlled by the presence of lithogenic minerals, aging processes and the build up of dSi in the pore waters. In particular, interactions between lithogenic silicate minerals and bSiO(2) may initiate rapid diagenetic alterations that favor the preservation of bSiO(2).